In last decade, high-speed signal transmission has already far exceeded the capability of copper cabling. The standard copper-based Ethernet networking is inadequate and replaced by fiber-optical communication system. Today's data centers are required to satisfy a large amount of activities, such as web-search, scientific computations, social networks, file storage and distributed file systems, inducing an unprecedented increase in data transmission. Data rates of 100 Gbps show their premium importance, which is even a challenge in fiber-optical network.
Due to its promise of high density integration, mature fabrication processing and compatibility with microelectronics, silicon photonics has attracted attention in optical telecommunication. In recent years, it has gradually become a promising technology offering high density and high speed data transmission.
Based on highly sophisticated silicon semiconductor technology, silicon photonic would provide an inexpensive integrated electronic-photonic platform, in which ultra-compact photonic devices and electronic circuits are converged. The low-cost high-volume photonic integrated circuits (PICs) with integrated electronics would simultaneously access the full potential for high-speed signaling and sensing, and subsequent logical operations and computations.
The PIC may consist of numerous scaled optical components, such as waveguides, MMIs, lasers and optical ring resonator. Waveguide is normally the most basic structure used for guiding light and interconnecting different elements on an optical chip. It also ensures the communications with outside by emitting the light and receiving it in turn. Of course, it should guarantee a sufficiently low propagation loss for constructing and integrating these photonic functions.
Silicon photonics packaging, which provides the substrate, support and protection to a silicon photonics system and also provides channel for data transmitting, is the assurance for a reliable communication. Much research has been done in the field. Used for telecom and datacom applications, fiber-to-PIC coupling is the most important aspect of photonic packaging. Many efforts have been made in order to improve the optical coupling efficiency.
In a transmitting system, good optical coupling efficiency is ensured by good alignment between the light from PIC and the optical fiber, or say, between the waveguide who guides the light and the optical fiber. In order to allow a relatively large tolerance of assembly and reduce the fiber assembly difficulty, an optical system is typically inserted between PIC and the fiber. Since the light from PIC inevitably has a radiation angle, a collimator lens is usually used in the system to make the light collimate and easy to be managed into the fiber with higher coupling efficiency. In miniature and compact PIC systems, the assembling of the collimator lens with the PIC by precise alignment is a challenge. Normally, active alignment method is used for this assembly. Active alignment here means aligning the components with some feedback indicating whether adjustment is needed for the alignment.
Hence, there is a need to provide an improved fabricating and alignment method for silicon photonics packaging.